Elbow lock mechanism



Oct. 30, 1951 J. H. LAMBERT 2,573,032

ELBOW LOCK MECHANISM Filed Dec. 5, 1947 Win-2:15.11

I N V EN TOR. Jof//v f6( IMBERT Patented Oct. 30, 1951 UNITED STATES PATENT OFFICE ELBOW LOCK MECHANISM Application December 5, 1947, Serial No. 789,955

8 Claims.

This invention relates generally to prosthetic devices and particularly to an artificial arm for use by above-the-elbow amputees. Specifically, the invention pertains to improved means for pivotally connectingthe upper arm member and forearm member of the artiiicial limb and means for frictionally locking the two members in different positions of angular adjustment.

In artificial limbs, particularly artificial arms for use by above-the-elbow amputees, the upper arm and forearm are pivotally connected by an elbow joint and through a system cf cords forming part of a harness worn by the amputee and connected to the forearm, the latter may be pivoted to different angles with respect to the upper arm. When such a structure is used, any weight lifted or supported by the artificial arm tends to pivot the forearm at the elbow and such tendency is resisted by the harness cords. Since the weight force is counteracted by the cords, the latter are subjected to considerable strain and this results in discomfort to the amputee. To avoid such a condition, various types of elbow locking devices have been suggested but such devices have not been altogether satisfactory for the reason that they are complicated in structure, add considerable weight to the arm, and are not readily operated by the amputee.

It is one object of my invention to provide an articial arm for use by above-the-elbow amputees, in which the upper arm and forearm are pivotally connected by an improved pivot or hinge-joint, the joint being of simple, light- Weight construction and yet sturdy and reliable in use. This object is attained by employing a light-weight tubular hinge pin or spindle of relatively large diameter so as to provide adequate bearing surface contact, the spindle being secured between upwardly projecting straps of the forearm and rotatably disposed in aligned apertures of a hollow upper arm member.

Another object of the invention is to provide in an arm, of the character referred to, an eiiicient locking means for frictionally resisting relative pivotal movement between the upper arm member and the forearm member so as to retainsaid members in different positions of angular adiustment. In a preferred embodiment of the invention .an expansible, contractible locking element surrounds the hinge-pin or spindle and normally is contracted to grip the spindle to effectively resist relative pivotal movement of the upper arm and forearm members. The locking element preferably includes a pair of torsion springs embracing the spindle and each having its outer ends connected to the upper arm member` and each having its inner ends projecting tangentially from the spindle at one side thereof. Operating means, in the form of a rotatable cam, is disposed within the upper arm member and between the projecting ends of the springs so that rotation of the cam spreads these ends apart to cause increase in the diameter of the springs so as to release the spindle and thereby permit relative rotation between the upper and forearm members of the limb.

Itis a further object of the invention to provide means whereby the operating cam may be conveniently and easily rotated by the amputee when it is desired to change the elbow angle.

A further object is to provide in an artificial arm and elbow locking means which is relatively simple in construction, positive in action and strong and durable in use.

Another object is to provide an elbow locking device, of the character referred to, which is adapted to be operated either by the sound hand of the wearer of the artificial arm or by a cable connection between the device and the shoulder of the wearer.

A still further object is to provide a locking device of the class specified in which the frictional locking means is adapted to yield in response to external shock loads imposed against the arm so as to prevent damage to the artificial arm and possible iniury to the amputee,

Further objects will appear from the following speciiication and the drawing, which is intended for the purpose of illustration only, and in which:

Fig. 1 is a perspective view of an artificial arm constructed in accordance with my invention;

Fig. 2 is a cross-sectional view of the elbow joint, taken on line 2 2 of Fig. 1;

Fig. 3 is a vertical sectional view, taken on line 3 3 of Fig. 2;

Fial 4 is a cross-sectional view through an elbow ioint of an alternative construction: and

Fia. 5 is a sectional view taken on line 5-5 of Fig. 4.

Referring to Figs. 1 to 3 of the drawing in detail. mv improved artificial arm includes an upper arm member 5 and a forearm member 6 pivotally connected at 1 to provide the elbow of the arm. The upper arm member 5 is preferably constructed from light-weight material such as molded plastic and is tubular throughout its leneth. The upper arm member 5 may be suitably attached to the upper arm stump of the amputee or may be of a lenath and shape suitable for attachment to the shoulder, the shape of the upper arm member and the attaching means therefor being unimportant since the present invention is directed particularly to the means for pivotally connecting and locking the upper arm and forearm members together.

The upper arm member 5 has a metal closure cap 9 at its lower end which may be molded in place, the cap having an axial hole for receiving a pivot screw Ill (Fig. 3). Connected to the lower end of the arm member 5 is a cuplike extension or elbow member I2 which consists of a horizontal disc portion I3 and depending side iianges I4, the opening between the flanges being closed by a detachable closure element Iii. The disc portion I3 has an axial hole for receiving the reduced shank portion of a nut I'I which is screwed onto the lower threaded end of the pivot screw i0. A friction washer I8 is interposed between the cap 9 and the disc portion I3 so that by tightening the nut il the two members 5 and I2 are drawn firmly together to resist considerable torque.

The forearm member 5 may also be made from plastic material and preferably is of tubular form. Secured to the inner wall of the forearm member 6 are oppositely disposed metal fingers or straps 2% which project upwardly above the upper end of the member and which have aligned apertures adjacent their upper ends for receiving headed screws 2l. The screws 2l are screwed into the threaded ends of a spool-like support 22 to rigidly secure the latter between the straps 2S. Surrounding the support 22 is a tube 23, herein-V after referred to as an elbow pivot bolt or spindle. rIhe length of the spindle 23 is such that when the screws 2I are tightened the spindle is firmly clamped between the straps 2i! of the forearm member 5. The ends of the tubular spindle 23 are rotatably held in aligned bearing apertures 24 in the depending side flanges Ill of the elbow member i?. so as to permit relative pivotal movement between the upper arm and forearm members 5 and 5. At least one of the straps is provided with an ear 25 which is adapted to engage against a shoulder 2G, as shown in Fig. l, to limit relative pivotal movement of the upper and forearm members in a direction to uniex the elbow or, in other words, to straighten the arm.

In addition to the improved pivotal connection between the upper arm and forearm members, the present invention provides means, to be next described, for frictionally locking these members to resist relative pivotal movement therebetween. The elbow locking means includes a pair of torsion springs 35 and SI which are slightly smaller in inside diameter than the outside diameter of the spindle 23 so that when the spindle vis forced through the aligned springs Sil and 3l, Aas shown in Fig. 2, the springs will, by virtue of their invherent contractibility, firmly grip the periphery of the spindle. The outer ends of the lsprings 3G and 3|, that is, theends adjacent the side flanges Is of the elbow member I2, are secured, as by welding to holders 32V. The holders 32 are fastened against the inner surfaces of the flanges I i by means of screws 33 (Fig. 3) so that the outer ends of the torsion springs 38 and 3| are held against rotation with respect to the upper arm member 5.

The torsion springs form, in effect, a clutch element, and their coils are wound in opposite directions, that is, one has a right-hand lead and the other has a left-hand lead. By this provision, the inner adjacent ends of the springs 36 and 3l extend in opposite directions and theQ G ILQS, 35

and 3S project tangentially from the spindle 23, at one side thereof, in converging relation. At their extremities, the projecting ends 35 and 35 are bent so as to provide parallel fingers 3l and 38 (Fig. 3), the inherent resiliency of the springs tending to move the fingers toward each other.

Rotatable in aligned holes in the flanges I4 are the ends of a shaft 4S which is provided with a relatively flat cam II disposed between the ends 3l and 3B of the torsion springs 3l) and 3l. The shaft l may be made in two sections l2 and i3 as shown in Fig. 2 to facilitate assembly and disassembly of the shaft within the elbow member I2. The shaft section l2 projects outwardly fromrthe side of the elbow member I2 and keyed to this projecting end is a finger-piece or handle 5 which may be conveniently turned by the ingers of the amputees sound arm to rotate the cam shaft from the position shown by full lines in Fig. 3 to that indicated by dotted lines. It is thus seen that 4by turning the shaft di? to the dotted line position, the cam 4I is caused to spread the ends 3l and 38 of the torsion springs apart and, since the outer ends of the springs are fixed, spreading of the ends 31 and 38 creates a torsional force tending to eX- pand the coils of the springs so as to relieve the frictional engagement of the springs against the periphery of the spindle 23 to permit relative pivotal movement between the upper arm and forearm members 5 and E. Preferably, a spring detent lil is secured to the disc portion I3 of the elbow member I2 by the nut Il and its end is adapted to engage an edge of the cam 4I to retain the latter in the inoperative position shown by full lines in Fig. 3.

Assuming that the artificial arm is extended, that is, with the upper arm and forearm in substantial alignment, and that the cam lil assumes the position shown by full lines in Fig. V3, the elbow will their be locked. That is to say, the torsion springs Sii and 3| will, by their inherent ability to contract in diameter, firmly grip the periphery of the spindle 23 so as to effective-A ly resist turning of the spindle and thus prevent relative pivotal movement of thev upper arm and forearm in a direction to cause fiexure of the elbow. However, when an external force ofv relatively great magnitude is applied suddenly against the forearm, the springs 30 and 3l will yield suiciently to permit flexing of the elbow and thereby prevent damage to the artificial arm and possible injury to the amputee. When it is desired to ex the arm, the shaft lll and cam @I are turned ninety degrees by means of the finger-piece #l5 so that the ends 35 and 36 of the torsion springs are spread apart to cause expansion of the springs. By this action, the friction 4of the springs against the spindle is relieved so that rotation of the spindle is permissible and the forearm may pivot with respect 'to the upper arm to ex the articial arm at the elbow. After the arm has been iiexed to the desired degree, the cam 4I is returned to the position shown by full lines to permit the torsion springs 30 and 3l to again bind around the spindle' 23l to retain the parts in this position of angular adjustment. It is thus seen'that by the simple act of pivot-v ing the finger-piece 45, 'the 'locking'means may be operated to lock and unlock the elbow. It will also be apparent that because the lockingl springs 30 and 3! frictionally engage the spindle 23, relative pivotal movementV between the upperY arm and forearm may 'be permitted when the.

5. forearm is subjected to a force greater than frictional resistance or braking action of the springs.

Referring now to Figs. 4 and 5, the present elbow locking device may be constructed in accordance with the modification therein shown. In this alternative structure, the upper arm member 5i) and the forearm member 5l are pivotally connected by the tubular spindle 52 which is held in place in an elbow member 53 carried at the lower end of the upper arm 'member by a tubular support 54 and screws 55. Surrounding the tubular spindle 52 is a pair of torsion springs 51 and 58 which normally grip the spindle with considerable force, the springs having radially extending ends 59 and 60, respectively.

Rotatable in aligned holes in the opposite sides of the elbow member 53 are the ends of a camshaft 62, the shaft being preferably made in two sections 53 and 54 to facilitate assembly and disassembly of the shaft. The shaft section 63 is provided with a relatively flat cam 65 which is disposed between the ends 59 and 50 of the respective springs 5'! and 58 and adapted, when rotated to one position, to spread these ends apart so as to expand the springs and permit relative pivotal movement between the upper Aarm member 5B and the forearm member 5l in the manner previously explained in connection with the embodiment illustrated in Figs. 1, 2 and 3. A leaf spring 65 engages the cam 65 and normally acts to retain the cam in inoperative position so that the springs 5T and 58 grip the spindle 52.

Rotatable on the shaft section `53 adjacent the cam 65 is a lever 58 which has secured thereto one end of a coil spring 63 surrounding the shaft section. The spring 69 forms, in effect, a resilient one-way clutch and acts, when the lever 58 is pivoted in one direction, to rotate the shaft section G3 and to slip circumferentially of the shaft section when the lever is pivoted in the opposite direction. A torsion spring 'lil surrounds the shaft section 63 and has one of its ends engaging against the interior of the upper arm member 5i! and its other end hooked through a hole in the lever 58 (Fig. 5). Looped through a hole in the end of the lever 58 is one end of a cord or cable 12, the cable extending through a hole 'i3 in the elbow member 53 and being preferably connected to a shoulder strap or other operating device capable of being manipulated by the wearer in response to a shrug of the shoulder.

The alternative elbow lock shown in Figs. 4 and 5 is operated in substantially the same manner in which the device illustrated in Figs. 1 to 3 is actuated. When the cord l2 is pulled, the lever 68 is pivoted in counterclockwise direction, as viewed in Fig. 5, and its spring 59 grips the shaft section 53 to rotate the latter and dispose the cam S5 crosswise between the ends 59 and 50 of the respective springs 5l and 58, such rotation of the shaft section and cam being against the action of the spring 70. In this manner, the springs 5i and 58 are expanded in diameter so as to free the spindle 52 and permit relative pivotal movement between the upper arm member 55 and the forearm member 5I. When the cord l2 is released, the spring 'l0 acts to return the lever 55 to first position with its clutch spring 59 slipping on the shaft section 63.

While I have herein shown and described the improved artificial limb as embodied in two preferred forms of construction, by way of example,

it will be apparent that various changes might be made therein without departing from the spirit of the invention. Consequently, I do not wish to be limited to the exact embodiments herein disclosed but desire to be afforded the full scope of the appended claims.

I claim as my invention:

1. In an artificial limb including two members connected for relative pivotal movement: a pivot spindle carried by the first of said members and rotatable in a bearing aperture of the second of said members; a torsion spring surrounding said spindle and having one end operatively connected to said second member and the other end projecting tangentially from said spindle, said spring having an internal diameter slightly smaller than the diameter of said spindle to adapt said spring to frictionally grip said spindle by its inherent contractibility so as to resist relative pivotal movement between said rst and second members; and manually operable cam means rotatable on an axis extending parallel to 'said spindle and engageable with said other end for moving the same in a direction tending to unwind said coil spring so as to release said spring from said spindle to permit free relative pivotal movement between said first and second members, said manually operable means including a rotatable cam engageable with said projecting end of said spring.

2. An artificial limb as defined in claim 1, in which said manually operable means includes: a shaft rotatable on said second member on an axis extending parallel to said spindle; and a cam on said shaft engageable with said projecting end of said spring.

3. An artificial limb as defined in claim 2, in which said manually operable means also includes handle means carried by said shaft for rotating same.

4. An artificial limb as defined in claim 3, and includingdetent means on said second member engageable with said cam for releasably retaining the same in position to permit contraction 0f said torsion spring.

5. In an artificial limb including two members connected for relative pivotal movement: a pivot spindle carried by the first of said members and rotatable in a bearing aperture of the second of said members; a pair of torsion springs surrounding said spindle, each spring having one end operatively connected to said second member and each spring having its other end projecting tangentially from said spindle, the projecting ends of said springs being disposed at the same side of said spindle and projecting from juxtaposed portions of said springs, said springs having internal diameters slightly smaller than the diameter of said spindle to adapt them to frictionally grip said spindle by their inherent contractibility so as to resist relative pivotal movement between said iirst and second members; and cam means disposed between said projecting ends and rotatable on an axis extending parallel to said spindle, said cam means being adapted upon rotation to spread said projecting ends apart so as to expand the coils of said springs to permit free relative pivotal movement between said first and second members.

6. In an artificial limb, the combination of: a first tubular member having projecting straps at one end; a second tubular member having aligned apertures in its side walls; a spindle extending between said straps and through said apertures to connect said rst and second members for relative pivotal movement; a pair of juxtaposed torsion springs surrounding said spindle within said second member, the coils of said springs being of opposite lead, each spring having its outer end secured to one of said side walls and its inner end projecting tangentially from said spindle, both of said projecting ends being disposed at the same side of said spindle, said springs having internal diameters slightly smaller than the diameter of said spindle to adapt them to frictionally grip said spindle by their inherent contractibility so as to resist relative pivotal movement between said iirst and second members; and cam means disposed between said projecting ends and rotatable on an axis extending parallel to said spindle, said cam means being adapted upon rotation to spread said projecting ends apart so as to expand the coils of said springs to permit free relative pivotal movement between said first and second members.

7. In an artiiicial limb including two members connected for relative pivotal movement: a pivot spindle carried by the first of said members and rotatable in a bearing aperture or the second of said members; a pair of torsion springs surrounding said spindle, each spring having one end operatively connected to said second member and each spring having its other end projecting tangentially from said spindle, the projecting ends of said springs being disposed at the same side of said spindle, said springs having internal diameters slightly smaller than the diameter' of said spindle to adapt them to frictionally grip said spindle by their inherent contractibility so as to resist relative pivotal movement between said first and second members; a shaft disposed parallel to said spindle and provided with a cam arranged between said other ends of said torsion springs, said cam being adapted upon rotation of said shaft in one direction to spread said ends apart so as to expand the coils of said springs to permit free relative pivotal movement between said first and sec- 0nd.' members; oneewav` clutch means for rotating said shaft in said onev direction; and spring means for returning said shaft and said cam to first position` 8. In an artificial limb including two members connected for relative pivotal movement: a pivot spindle carried by the rst of said members and rotatable in a bearing aperture of the second of said members; a pair of torsion springs surrounding said spindle, each spring having one end operatively connected to said second member and each spring having its other end projecting tangentially from said Spindle, the projecting ends of said springs being disposed at the same side of said spindle, said springs having internal diameters slightly smaller than the diameter of said spindle to adapt them to frictionally grip said spindle by their inherent contrafritibility so as to resist relative pivotal movement between said first and second members; a shaft disposed parallel to said spindle and provided with a cam arranged between said other ends of said' torsion springs, Said cam Abeing adapted; upon rotation of said shaft in one direction to spread said ends apart so as toexpand the coils of said springs to permit free relative pivotal movement between said rst and second members; a manually operable lever rotatable on said shaft; a coil spring secured to said lever and surrounding said shaft, said coil spring being adapted to rotate said shaft and cam inV saidone direction when said lever is rotated in the same direction; and spring means for returning said shaft and said cam to rst position.

JOHN H. LAMBERT.

REFERENCESl CITED FOREIGN PATENTS Country Date Great Britain 1922 Number 

